Examined Japanese Patent Publication HEI 1315059 discloses a device which is known as such a cassette loading device. In the following description, one side of the device where a rotary cylinder 800 is provided will be referred to as "front," and the other side thereof where there is a cassette insertion-discharge position as "rear."
With reference to FIGS. 21 to 23 showing the disclosed device, a chassis 100 has a pair of side plates 762, 763 thereon, and a tray 765 for holding a cassette thereon is disposed between the two side plates 762, 763 and in the rear of reel supports 200a, 200b. A top plate 775 is connected between the upper ends of the side plates 762, 763 as indicated in broken lines. A front panel 770 attached to the rear end of the chassis 100 has a height approximately equal to the height of the upper surface of the top plate 775 from the upper surface of the chassis 100.
Opposite sides of the tray 765 are bent upward to provide cassette holding plates 771, 771. Each cassette holding plate 771 has two projections 765a, 765b projecting therefrom sideways. The projections 765a, 76b fit respectively in approximately L-shaped guide grooves 764, 772 which are formed in each of the side plates 762, 763. The cassette is in an insertion-discharge position when the projections 765a, 765b are in contact with the rear ends of the respective grooved portions 764, 772. The cassette is in a loaded position when the projections 765a, 765b are brought to the lower ends of the respective guide grooves 764, 772. The guide groove 772 comprises a slanting portion 772a slanting upward toward the front and a descent portion 772b extending from the front end of the slanting portion 772a downward as slightly slanted rearward and communicating with the slanting portion 772a. The guide groove 764 comprises a slanting portion 764a approximately parallel to the slanting portion 772a and a vertical portion 764b extending threfrom.
A gear lever 780 is supported by a shaft on the right side plate 763 and has an arm 780a. The arm has a pin 787 projecting outward from its forward end. A link 785 has one end fitting to the projection 765a on the tray 765 and the other end loosely fitting to the pin 787. The link 785 is connected to the arm 780a by a tension spring 786.
A bracket 759 is attached to the outer side of the side plate 763. On the outer face of the gear lever 780, a first gear 781 is mounted on the same shaft as the lever. By meshing engagement, the first gear 781 is coupled via an intermediate gear 783 to a second gear 782 which is disposed in front of the gear 781 and supported on the inner side of the bracket 759. The second gear 782 is in mesh with a rack piece 784 disposed thereabove and interposed between the side plate 763 and the bracket 759. Flanged guides 164, 164 projecting inward from the bracket 759 fit respectively in slots 784a, 784b formed in the rack piece 784 and extending longitudinally thereof, whereby the rack piece 784 is made slidable forward or rearward. The two side plates 762, 763, first gear 781, intermediate gear 783 and second gear 782 constitute a front mechanism 760.
When the rack piece 784 slidingly moves forward, the second gear 782 rotates clockwise, rotating the first gear 781 and the gear lever 780 also clockwise. The rotation of the gear lever 780 advances the projection 765a in engagement with the link 785. The tray 765 slidingly moves as slightly inclined along the slanting portion 764a of the guide groove 764 and along the slanting portion 772a of the guide groove 772, and further descends along the vertical portion 764b of the guide groove 764 and the descent portion 772b of the guide groove 772 while correcting its inclination by rotating about the projection 765a. Upon the projections 765a, 765b reaching the lower ends of the respective guide grooves 764, 772, the cassette comes into contact with a cassette support 604 on the chassis 100.
When the first gear 781 further rotates clockwise, the gear lever 780 stretches the tension spring 786 provided between the lever 780 and the link 785, biasing the tray 765 downward through the projection 765a. Accordingly, the cassette 600 is pressed against the cassette support 604 and made ready for the subsequent tape loading.
FIGS. 24 to 25B show another device already proposed in which the tray 765 has three projections 765a, 765b, 765c projecting from a side portion thereof and engaged in a guide groove 778 in the side plate 763 or engaged with a slide piece 776 having a cam 777 (see Examined Japanese Patent Publication SHO 63-119061). The mechanism for slidingly moving the tray 765 is known and therefore will not be described, and how the tray 765 is guided will be described.
The projection 765a is provided on a rear end side portion of the tray 765, while the projections 765c, 765b are arranged obliquely upwardly away from the projection 765a. On the inner side of the side plate 763, the slide piece 776 having the cam 77 is slidably provided in engagement with slotted portions 753, 754 of the slide plate 763 which extend vertically. The cam 777 has an upper face including a horizontal portion 777a extending from the rear end of the slide piece 776 forward, a slanting portion 777b extending from the front end of the horizontal portion 777a obliquely upward and an upper horizontal portion 777c horizontally extending from the upper end of the slanting portion 777b, these cam face portions being continuous with one another. The cam 777 has a lower face which is generally parallel to its upper face but has a recessed portion 777d corresponding to the slanting portion 777b.
The guide groove 778 includes a horizontal groove 778a formed in the rear end of the side plate 763, a slanting groove 778b extending from the front end of the horizontal groove 778a and approximately parallel to the slanting portion 777b of the cam 777 and a descent groove 778c extending downward from the upper end of the slanting groove 778b, the grooves 778a to 778c being in communication with one another. The projection 765b is in contact with the upper face of the cam 777, and the projection 765c with the lower face of the cam 777. The projection 765a is slidingly movable along the guide groove 778.
When the cassette is loaded, the projection 765a moves along the horizontal groove 778a and the projection 765b along the upper face of the horizontal portion 777a, followed by movement of the projection 765a along the slanting groove 778b and movement of the projection 765b along the slanting portion 777b. Accordingly, the tray 765 moves along as inclined.
Upon the projection 765b reaching the upper horizontal portion 777c, the projection 765c reaches the recessed portion 777d with the projection 765a fitting in the slanting groove 778b. As the tray 765 advances, therefore, the tray 765 rotates clockwise about the projection 765b and has its inclination corrected to a horizontal position. With the tray in this position, the projection 765a moves down the descent groove 778c, so that the slide piece 776 descends along the slots 753, 754 for the cassette to reach a loaded position.
The cassette loading devices described have the following problems.
1. When the cassette 600 as completely loaded in position is held pressed against the cassette support 604 by the tension spring 786, the rack piece 784 is subjected to the load of holding the cassette 600 pressed. With magnetic recording-reproduction apparatus of the type described, the parts of the tape running system are driven generally by a cam mechanism for driving the rack piece 784, so that an increased load acts on the cam mechanism when the parts are driven.
2. It is strongly desired in recent years that magnetic recording-reproduction apparatus having a cassette loading device be made thinner, and it is necessary to limit the height from the upper surface of the chassis 100 to the upper end of the front panel 770. With the device shown in FIGS. 24 and 25, the tray 765 moves horizontally along the guide groove 764, so that the cassette inlet opening in the front panel 770 needs to be positioned at a higher level than the reel supports. This prevents thinning.
Further with the device shown in FIGS. 21 to 23, the inclination of the cassette is corrected by rotation about the projection 765a close to the cassette insertion-discharge side. This involves a great horizontal shift of the front end portion of the cassette 600 to result in the likelihood that the magnetic tape will become caught by guides for transporting the tape.
3. With the cassette loading device shown in FIG. 24, the cassette 600 is raised to a corrected horizontal position and thereafter lowered during loading. This reduces the clearance between the upper surface of the cassette 600 and the top plate 775 provided between the side plates 762, 763, over a large area. Consequently, there is a need to thin the top plate 775 over this area or partly cut out the top plate 775 so as to avoid the contact of the cassette with the top plate 775 while satisfying the need to thin the recording-reproduction apparatus. This results in a reduced strength.
4. If the flanged guide 164 for supporting the rack piece 784 is formed by slitting the chassis 100, the rack piece 784 is likely to engage with burrs, failing to move smoothly. A screw or the like, if used, adds to the number of parts.
As shown in FIG. 26, the flanged guide 164 may be formed on an abutment plate 161 by outsert molding using two molds 865, 866 as arranged on opposite sides of the chassis 100. The mold 865 is inserted through an opening in the chassis 100 from above, while the other mold 866 is fitted to the lower end of the abutment plate 161 and contacted with the bottom of the mold 865. A molten resin is filled into a space between the two molds 865, 866 through an injection channel 862 and cooled, whereby the flanged guide 164 is formed.
However, since the abutment plate 161 is formed by bending the chassis 100, variations in the degree of bending work accuracy entail the likelihood that the mold 866 will not smoothly fit to the abutment plate 161, presenting difficulty in molding. Furthermore, the mold 866 is likely to become caught by burrs produced on the edge of the abutment plate 161 and becomes difficult to remove.